1. Field of the Invention
The present invention relates to the fields of field programmable gate array (FPGA) and emulation systems.
2. Background Information
Emulation systems for emulating circuit design are known in the art. Typically, prior art emulation systems are formed using general purpose FPGAs without integrated debugging facilities. A circuit design to be emulated is "realized" on the emulation system by compiling a "formal" description of the circuit design, and mapping the circuit design onto the logic elements (LEs) of the FPGAs.
These general purpose FPGAs, as far as their applications to emulation systems are concerned, have a number of disadvantages. First of all, the states of signals at the nodes mapped inside the FPGAs are not directly observable, thus the term "hidden" nodes. Secondly, in order to be able to observe the states of signals at these "hidden" nodes, reconfiguration, and therefore extremely time consuming recompilation is required to bring these signals outside the FPGAs to a logic analyzer. Thirdly, a number of the FPGA I/Os will have to be consumed for bringing these signals to the logic analyzer. Furthermore, the additional signals to be routed further increase signal routing congestion. Finally, for timing sensitive applications, it is difficult to know whether the signals at these "hidden" nodes were read at precisely the correct time or not, if the signals are to be read in response to the occurrence of certain events, since the signals have to be brought out of the FPGAs before the read triggering events can be detected.
Thus, it is desirable to have an improved FPGA with integrated debugging facilities that is more suitable for usage by the emulation systems. As will be described in more detail below, the present invention provides for such an improved FPGA with integrated debugging facilities that achieves these and other desired results, which will be apparent to those skilled in the art from the description to follow.